Method and Apparatus for Power Saving in Wirelless Systems

ABSTRACT

A method is provided for carrying out a power saving procedure in a wireless subscriber terminal which is operative to receive at least two different services, each of which is characterized by one or more characteristics related to traffic demands associated with that service. The method comprises the following steps: classifying each of the at least two different services based on their traffic demand related characteristics into corresponding power saving classes, where there are at least two different power saving classes associated with the at least two different services; for each of the power saving classes, determining required listening windows and required sleep windows; exchanging messages between the base station and the subscriber&#39;s device for synchronizing parameters for carrying out the power saving procedure.

FIELD OF THE INVENTION

The present invention relates generally to digital communications, andin particular, to the field of power saving.

BACKGROUND OF THE INVENTION

“Draft IEEE Standard for Local and metropolitan area networks, Part 16:Air Interface for Fixed and Mobile Broadband Wireless Access SystemsAmendment for Physical and Medium Access Control Layers for CombinedFixed and Mobile Operation in Licensed Bands”, published on Sep. 18,2004 will be referred herein as “IEEE 802.16 publication”. Thedisclosure of this reference is hereby incorporated herein by reference.The IEEE 802.16 publication is an international recommendation, which isbeing adopted for combined fixed and mobile operations. In an attempt toachieve efficient power utilization, a “sleep mode” procedure has beendefined by that standard. This sleep mode procedure comprises virtuallyinfinite sequence of listening windows (where the subscriber's terminalis ready to communicate with a base station) interleaved with sleepwindows (where the terminal may power down so as to reduce the level ofconsumed power). According to this recommendation, the duration of eachof the listening windows has a fixed size, while the duration of thesleep windows doubles in size, up to a certain limit. This proceduregives an adequate solution to cases where “random” traffic is conveyed,e.g. “bursty” IP traffic, like WEB browsing. Such traffic is typicallycharacterized as being associated with non-real time MAC connections andbest efforts type connections.

However, a problem arises when different types of services are renderedby a base station to a plurality of subscribers' terminals associatedtherewith, while the sleeping mode procedure is suitable for a singletype of service having a random nature. Such a sleeping mode procedurecannot be adequately applied for services such as voice/VoIPapplications on one hand and some other real time applications on theother, as the latter would typically have different patterns than theabove-described ones, and consequently such a sleep mode procedurecannot be applicable for all these services.

Having to provide multicast/broadcast services to the differentsubscribers together with, say, having to provide WEB browsing services,would impose a problem as it will be virtually impossible to handle thedifferent types of services while applying a single type of sleep modeprocedure provided by the IEEE 802.16 publication.

Another problem arises in systems that support multicast services.Typically, the terminals are designed to have both multicast connectionsand unicast connections with different demand patterns, so thatsynchronization of sleep/listening cycles between different terminalswould be nearly impossible. Under the IEEE 802.16 publication's sleepmode scheme, the only reasonable solution is to interrupt the sleep modefor all relevant terminals and to arrange for data transfer. The penaltyassociated with interrupting terminals in their sleep mode, is, that theinterrupted terminal would be re-activated from the lowest value of thesleep window, which in turn causes a decrease in the efficiency of powersaving.

Yet another problem that arises is when there is a need to combine thesleep mode operations with one or more management procedures likeranging, connections creation/configuration, SNMP etc. Suppose that aterminal is currently at a sleep mode as there is no traffic to bedelivered via the existing connections and there is a need to add onemore connection. In this case, the base station (“BS”) has to keep theterminal available for the corresponding transaction, although there isstill no demand for using the existing connections, which means thatthere is in fact no reason to interrupt their sleep state. But in spiteof the above, according to the procedure that has been commonly used inthe art, the sleep mode of the terminal will be interrupted by “TrafficIndication” message (even though, as explained above, there is notraffic to be conveyed along the current connections), for applying theconnection creation procedure. Consequently, the sleep mode procedurewill have to be re-applied, from the lowest sleep window value.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a novelmethod for carrying out power saving by minimizing the power consumptionat mobile terminal.

It is another object of the present invention to provide a novel methodfor controlling the power consumption at mobile terminal so as toprovide a higher efficiency of power utilization.

It is yet another object of the present invention to provide a methodfor carrying out power saving by minimizing the power consumption atmobile terminal which is adapted to provide several services havingdifferent power requirement patterns.

Other objects of the invention will become apparent as the descriptionof the invention proceeds.

It is therefore provided in accordance with a first embodiment of theinvention, a method for effecting power saving at a subscriber's devicebelonging to a wireless network which comprises a base station and atleast said subscriber device, wherein said subscriber's device isadapted to receive at least two different services, each of which ischaracterized by one or more characteristics related to traffic demandsassociated with that service.

The method comprises the following steps:

classifying each of the at least two different services based on theirtraffic demand related characteristics, into corresponding power savingclasses, provided that there are at least two different power savingclasses associated with services supported by the subscriber's device;

for each of the power saving classes, determining the required listeningwindows and the required sleep windows;

exchanging messages between the base station and the subscriber's devicefor synchronizing the parameters for carrying out a power savingprocedure. Such parameters preferably comprise the location of thelistening/sleep windows in the time domain and conditions forterminating the whole procedure (for example, if a demand does appear atone of the connections). More preferably, the set of parameters includesa starting point for effecting the sequence of sleep/listening windows.No communication is assumed during sleep window with respect to services(connections) associated with the corresponding power saving class.

As will be appreciated by those skilled in the art, the step ofclassifying each of the at least two different services, can be carriedby implementing any one or more of a variety of options, such as beingbased on the type of the service, based on the traffic demand pattern,based on the group of services to which the particular service belongs,etc., all of which should be understood to be encompassed by the presentinvention.

Next, during the provisioning of the different services, determining anunavailability window of time for the subscriber's device (e.g. themobile terminal) in which no communication will be exchanged between thebase station and the subscriber's device, i.e. the window at which allservices associated with the terminal are inactive; and then

reducing the power level at the subscriber's device, for the duration ofthe unavailability window(s).

The term “power saving class” as used herein, is used to denote a groupof one or more services comprising one or more MAC connections(services), all of which are characterized as having similar traffic(demand) behavior, and wherein all of these connections are comprised ina single power saving class, and will be associated with the samesequence of listening and sleep windows. If we consider for example,that WEB browsing (service A) and communication to remote file server(service B) have the same traffic (demand) behavior, they may beassociated with a single power saving class. However, it may happen thateven though two services have the same type of traffic behavior, stillthe parameters of the traffic behavior are different, in which case eachof the two services shall belong to a different power saving class.

According to a preferred embodiment of the invention the method providedmay be initiated by the subscriber's device, upon transmitting a requestfor the initiation of a power saving procedure. Still, the finaldecision on the activation of power saving class and its appropriateparameters is preferably made by the BS.

In accordance with yet another embodiment of the invention the powersaving class is selected from the group consisting of:

type 1 class, characterized in that the duration of each of the sleepwindows is derived from the duration of its preceding sleep window,while the duration of the listening windows remain constant;

type 2 class, characterized in that all sleep windows are of the sameduration and are interleaved with listening windows having fixedduration; and

type 3 class, characterized in that it comprises a single sleep windowand a single listening window.

Preferably, type 1 class of the power saving is further characterized inthat no traffic is allowed to be exchanged during the duration of thesleep windows and the listening windows.

By still another embodiment of the invention, type 2 power saving classis further characterized in that exchange of traffic is prevented duringthe duration of the listening windows.

According to yet another embodiment of the invention, type 3 powersaving class is further characterized in that no traffic is exchangedduring the duration of the sleep window.

In accordance with yet another aspect of the invention there is provideda controller for controlling the duration of the power saving periodallowed in the subscriber's device, and wherein preferably thecontrolling is done by deactivating the power saving class.

Preferably, when the service is of the type 1 class, the deactivation ofthe power saving class is carried out in response to the occurrence ofone or more of following events:

-   -   The BS transmits (during availability window) some amount of        data over a connection belonging to this Power Saving Class;    -   The terminal transmits a request for non-zero amount of        bandwidth with respect to a service (connection) belonging to        this Power Saving Class;    -   The terminal receives a message from the BS indicating the        presence of buffered traffic addressed to the terminal;    -   The terminal has failed to receive traffic indication message        during certain timeout interval, for example, during a listening        window.

In accordance with yet another embodiment of the invention, thedeactivation of the power saving class carried out in response toexplicit request initiated either by the BS or by the terminal.

By yet another embodiment of the invention, deactivating of the powersaving class for type 2 class of service is carried out in response toexplicit request (e.g. termination request) transmitted in the form ofpre-defined management messages from the BS and/or the subscriber'sdevice.

In accordance with yet another embodiment of the invention when theservice is of the type 3 class, the deactivation of the power savingprocedure is carried out in response to the expiration of a listeningwindow period.

According to another aspect of the invention there is provided a basestation adapted to operate in a wireless network and comprising:

an interface operative to allow communication between the base stationand a communication network associated therewith;

at least one radio transceiver capable of transmitting communicationtraffic towards at least one subscriber device and receive communicationtraffic therefrom, wherein the base station is adapted to provide thesubscriber with at least two different services, each of which ischaracterized by one or more characteristics related to traffic demandsassociated with that service;

means operative to classify each of the at least two different servicesbased on their traffic demand related characteristics into theircorresponding power saving classes, provided that there are at least twodifferent power saving classes associated with services supported by thesubscriber's device;

at least one processor adapted to:

for each of the power saving classes, determine required listeningwindows and possible sleep windows;

exchange messages with the subscriber's device for synchronizing atleast one parameter for carrying out a power saving procedure;

during provisioning of the at least two different services, determineunavailability windows of time for the subscriber's device in which nocommunication will be exchanged between the base station and thesubscriber's device; and

initiating commands whereby the subscriber's device is required toactivate a power saving procedure for the duration of the unavailabilitywindows.

According to yet another aspect of the invention there is provided asubscriber's terminal adapted to operate in a wireless network and toreceive at least two different services, each of which is characterizedby one or more characteristics related to traffic demands associatedwith that service, and wherein said subscriber's terminal comprising:

an interface operative to allow communication between the subscriber'sterminal and a base station;

at least one radio transceiver operative to transmit communicationtraffic towards the base station and receive communication traffictherefrom;

at least one processor adapted to exchange messages with the basestation for synchronizing at least one parameter for carrying out apower saving procedure; and

a power controller operative to effect a reduction in the power of theat least one radio transceiver for the duration of unavailabilitywindows of time in which no communication will be exchanged between saidbase station and the subscriber's terminal, in response to a pre-definedmessage received from the base station.

Preferably, the at least one processor is further adapted to initiate arequest for transmitting a communication to the base station, by whichthe base station is requested to evaluate whether, and/or when, thesubscriber's terminal may start a power saving procedure.

By another embodiment, the subscriber's terminal is further adapted toaffect a power saving procedure in response to an appropriate messageand/or a signal received from the base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of power saving procedure for a multicasttype of service;

FIG. 2 illustrates an example of power saving procedure for periodicranging; and

FIG. 3 illustrates an example of sleep operation mode with two powersaving types of classes, one associated with service (connection)carrying traffic of WEB type and another one associated UGS service(e.g., Voice over IP) described in the with IEEE 802.16 publication.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by way of examples, and withoutlimiting the generality of the foregoing.

According to a preferred embodiment provided by the present invention,the subscriber's terminal comprises multiple Sleep State Machines(“SSM”s), where the term “sleep state” refers to being in a sleep timewindow or in a listening window. Each one of the SSMs is associated witha Power Saving Class (“PSC”) that comprises one or more services all ofwhich are characterized by having a substantially similar traffic demandbehavior (e.g. demand for transmitting a packet when a packet that isdue for transmission arrives). Similarly, the Base Station (BS)comprises a set of SSMs that corresponds to that of the subscribers'terminals associated with that BS. The BS and the various subscribers'terminals exchange control messages in order to synchronize the state ofthe SSMs. Non-availability of a subscriber's terminal for downlink (DL)or uplink (UL) transmissions is defined as a state where all statemachines are in a “sleep” state. While being at a non-available state,the subscriber's terminal may power down one or more physical operationcomponents or perform other activities that are unrelated to itscommunication with the BS. According to an embodiment of the invention,the BS comprises all the SSMs required for the classes of servicessupported by the BS, while the SSMs comprised in the subscriber'sterminal are only those that correspond to the various classes to whichall the services offered by that terminal, belong.

Let us now consider FIG. 1 in which there is an illustration of anexample of a terminal having two SSMs, each of which corresponds to adifferent PSC. Class A comprises several services that can becharacterized as being of “Best Effort” type as defined in IEEE 802.16publication and as being non-real time type. Class B of this examplecomprises a single service, VoIP (defined as “UGS” in terms of IEEE802.16 publication). The BS allocates for Class A, a sequence oflistening windows each having a constant duration and doubling sleepwindows, i.e. each window (except for the first one following theactivation of power saving class) lasts twice the time of its precedingsleep window. For Class B, the BS allocates a sequence of listeningwindows, each of which has a constant duration of time and aninterleaved sequence of sleep windows, each again having a constantduration of time, not necessarily equal to that of the listeningwindows. The terminal is considered to be unavailable (and consequentlymay power down) within those periods of time that both Classes havetheir sleep windows, or in other words when the sleep windows of Class Aintersects with those of Class B.

By another preferred embodiment, the BS retains one or morelistening/sleeping schemes adapted for each of the subscribers'terminals associated with the BS, and wherein each one of the schemesrelates to a certain Power Saving Class (PCS). As previously explained,Power Saving Class is a group of MAC connections (services), which havecommon power demand properties. It will be appreciated by those skilledin the art, that all “Best Efforts” connections (e.g. as defined in theIEEE 802.16 publication) may belong to a single class, hence they willall have the same sleep/listening windows. On the other hand, therecould be cases where two UGS connections (services) may each belong to adifferent class, in the case that they are associated with differentintervals between consequent allocations. The meaning of activating acertain PSC is in fact the initiation of the sleeping/listening windows'sequence associated with that class. For the purpose of determining oneor several PSCs and/or activating them, the BS and the correspondingsubscriber's terminal exchange certain management messages therebetweenin order to specify the type and parameters of the applicable PCS andtime instance of activating the sleeping/listening windows' sequence.

After determining the possible sleeping windows for each of theapplicable services as described above, an unavailability intervals aredetermined as those for which all active SSMs are in “sleep” state.

The term “availability interval” is used herein to denote a timeinterval that does not overlap with any unavailability interval. Duringthe availability interval the terminal is expected to receive alldownlink (“DL”) transmissions by using the same scheme as the oneimplemented during normal operation (no sleep).

As mentioned hereinbefore, the second service provided by this exampleis VoIP (Class B). In this case, a demand for the transmission of afixed portion of data appears periodically, so that the terminal isprovided with listening windows having constant duration that will beapplied around the time instances in which the terminal is expected tobe operative (e.g. transmitting or receiving data), and sleeping windowsare provided in-between these listening windows. Data transmissionduring the listening windows' periods is preferably allowed withoutinterrupting the sleeping state. By this preferred embodiment, one ofthe disadvantages of the presently implemented sleep scheme is overcome,as there is no longer a need for the BS to terminate the sleepprocedure, arrange data transfer and restart the sleep procedure, everytime a VoIP demand appears.

A similar solution may be applied if Class B comprises a voice serviceinstead of the VoIP service discussed above.

Following is an example of a method implementing the present inventionwhere the BS is adapted to supply to the subscriber's terminal anycombination of services out of those classified in the following threeclasses.

Power Saving Class of Type 1:

Examples of network services associated with this type are WEB browsingand communication to remote file server.

In order to establish proper operability between the BS and asubscriber's terminal using any one of the services included in thisclass, the BS and the terminal exchange messages that specify at leastthe following parameters:

-   Initial-sleep window;-   Listening window;-   Final-sleep window; and-   Start time for the first sleep window.

The power saving scheme becomes active at the moment specified as Starttime for the first sleep window. The duration (size) of each one of thenext sleep windows may be derived from the size of its preceding sleepwindow. For example, each next sleep window may be twice the size of theprevious window, but provided it is not greater than the value of theparameter “Final-sleep window”. In addition, during listening windows,the BS may periodically transmit message(s) indicating thepresence/absence of buffered DL traffic addressed to the terminal.

Sleep windows are typically interleaved with the listening windows, asthe latter have fixed duration.

For example, the BS terminates active state by sending trafficindication message (e.g. MOB_TRF_IND in the IEEE 802.16 publication). Atraffic indication message shall be sent by the BS during each listeningwindow to alert the terminal that DL traffic demand appeared at thecorresponding connections.

When the terminal receives a UL allocation after receiving a positiveMOB_TRF-IND message indication, the terminal may confirm reception ofthe message by transmission of at least BR message.

During active state of Power Saving Class, the terminal is not expectedto send or receive any data (e.g. MAC SDUS) or to send bandwidthrequests at connections that belong to that Power Saving Class.

The Power Saving procedure becomes active at the time instant specifiedas Start time for first sleep window. Each next sleep window is twice ofsize comparatively to previous one, but not greater than specified finalvalue

Power saving procedure is deactivated in response to the occurrence ofone or more of following events:

-   -   The BS transmits (during availability window) a MAC SDU or        fragment thereof over connection belonging to this Power Saving        Class;    -   The terminal transmits a request for non-zero amount of        bandwidth with respect to a service (connection) belonging to        this Power Saving Class; and    -   The terminal receives traffic indication message (e.g.        MOB_TRF-IND in IEEE 802.16 publication) indicating presence of        buffered traffic addressed to the terminal.    -   The terminal fails to receive traffic indication message (e.g.        MOB_TRF-IND in the IEEE 802.16 publication) during a certain        timeout interval, for example, during a listening window.

During the listening windows, the terminal is expected to receive all DLtransmissions the same way as in the state of normal operations (nosleep).

Power Saving Classes of Type 2:

Examples of services associated with this type are UGS, RT-VR type asspecified in the IEEE 802.16 publication, e.g. connections (services) ofvoice (VoIP) and real-time services.

In order to establish proper interoperability between the BS and asubscriber's terminal using any one of the services included in thisclass, the BS and the terminal exchange messages that specify at leastthe following parameters:

-   Initial-sleep window;-   Listening window; and-   Start time of the first sleep window.

Power Saving Class of this type becomes active at the moment specifiedas “Start time of the first sleep window”. All sleep windows are of thesame size and are interleaved with listening windows having fixedduration. Once started, the active state continues until it isexplicitly terminated by terminating the associated connections(services) or by exchange of certain management messages, which specifythat termination.

Unlike the Power Saving Class of Type 1 that was described above, duringthe listening windows of Power Saving Class Type 2, the terminal maysend or receive any data at connections (services) that are included inthis Power Saving Class.

Power Saving Class becomes active at the frame specified as “Start timeof the first sleep window”. All sleep windows are of the same size asthe initial window. Sleep windows are interleaved with the listeningwindows having fixed duration. Power Saving procedures applied for thistype are defined/activated/deactivated by certain control messages (e.g.MOB_SLP-REQ/MOB_SLP-RSP transaction in the IEEE 802.16 publication). TheBS may send unsolicited message to initiate activation of Power Savingprocedure (e.g. MOB_SLP-RSP in the IEEE 802.16 publication). Onceinitiated, the active state continues until explicit termination byspecific messages like MOB_SLP-REQ/MOB_SLP-RSP in the IEEE 802.16publication. BS may send unsolicited message (MOB_SLP-RSP in the IEEE802.16 publication) to deactivate Power Saving Class.

As opposed to the procedure for Power Saving Class Type 1, the terminalmay send or receive data at connections associated with this type ofPower Saving Class, during the listening windows.

Power Saving Classes of Type 3:

Examples of services associated with this type are broadcast/multicastconnections as well as management operations such as, Ranging,connection setup/change/deletion. Power Saving Classes of this type aredefined/activated by certain management messages such asMOB_SLP-REQ/MOB_SLP-RSP transaction in the IEEE 802.16 publication.Deactivation of the PSC occurs automatically following the expiration ofthe listening window.

In order to establish proper operability between the BS and asubscriber's terminal using any one of the services included in thisclass, the BS and the terminal exchange messages that specify at leastthe following parameters:

-   -   Final-sleep window (which may be encoded as base/exponent);    -   Start time of the first sleep window; and    -   Listening window.

This Power Saving Class becomes active at the moment specified as “Starttime of the first sleep window”. Listening window of a specified sizewill follow the sleep window.

The listening window, which is of a specified size, follows the sleepwindow. Once the listening window expires, the power saving procedurebecomes automatically inactive.

FIG. 2 illustrates a method of using PSC of Type 3 associated withmulticast connection. In the provisioning of multicast service, the BSassumes when will the next portion of data appear. In accordance withthat assumption, the BS allocates a sleep interval that extends for thewhole period during which no multicast traffic is expected to arrive. Ifduring the listening window there is multicast data available, it willbe transmitted to the relevant terminals. Once the listening window hasexpired, the BS may take the decision whether to re-activate the PowerSaving Class.

Power Saving Class of type 3 may be used also for control procedureslike creation or deletion of MAC connections or ranging. In this case BStransmits request and specifies duration (e.g. base/exponent) of thesleep window being equal to the time interval needed before nextPeriodic Ranging transaction. Then the terminal, after a specified timeinterval has expired, shall be available to DL transmission and then theBS may either allocate a UL transmission opportunity for ranging.

Power saving procedure of this type will be automatically deactivatedafter all involved connections closed.

Sleep Request and Sleep Response Messages

Terminal supporting sleep procedure uses the MOB_SLP-REQ message torequest definition and/or activation of certain Power Save Classes oftypes 1 and 2. The MOB-SLP-REQ message is sent from the terminal to theBS on the terminal's Basic CID. TABLE 1 Sleep-Request message formatSyntax Size MOB_SLP-REQ_Message_Format( ) {   Management message type =50 8 bits   Number_of_Classes 4 bits   for (i = 0; i <Number_of_Classes; i++) {     Power_Saving_Class_Type 2 bits    Definition 1 bit      Operation 1 bits     If (Operation = 1) {      Start_frame_number 8 bits     }     if (Definition = 1) {      Initial-sleep window 8 bits       listening window 8 bits      final-sleep window base 10 bits        final-sleep window exponent3 bits       Number_of_CIDs 3 bits       for (i = 0; i < No._of_CIDs;i++)       {         CID 16 bits        }     } }The parameters used are as follows:Definition

1=Definition of Power Saving Class present

Operation

1=Activation of Power Saving Class

0=Deactivation of Power Saving Class (for types 1 and 2 only)

Power_Saving_Class_ID

Assigned Power Saving Class identifier. The ID shall be unique withinthe group of Power Saving Classes associated with the terminal. This IDmay be used in further MOB_SLP-REQ/RSP messages foractivation/deactivation of Power Saving Class.

Start_Frame_Number

Start frame number for the first sleep window.

Listening Interval

Assigned Duration of the terminal's listening interval (measured inframes). For power saving class type 2 it is not relevant and must beencoded as 0.

Initial-Sleep Window

Assigned initial duration for the sleep window (measured in frames). ForPower Saving Class type 2 it is not relevant and must be encoded as 0.

Final-Sleep Window Base

Assigned final value for the sleep interval (measured in frames). ForPower Saving Class type 2 it is not relevant and must be encoded as 0.For Power Saving Class type 2 it is the base for duration of singlesleep window requested by the message.

Final-Sleep Window Exponent

Assigned factor by which the final-sleep window base is multiplied inorder to calculate the final-sleep window. The following formula isused:final-sleep window=final-sleep window base×2ˆ(final-sleep windowexponent)

For power saving class type 2 it is the exponent for the duration ofsingle sleep window requested by the message.

CID

CIDs of all connections comprising the Power Saving Class. This listshall contain either unicast connections, multicast connections ormanagement connections, but not combination of connections of differenttypes. If basic CID is encoded, it means that all the terminal'sconnections are included in a single class.

-   CID=0 is reserved for management operations.

The MOB-SLP_RSP message shall be sent from the BS to the terminal on theterminal's Basic CID in response to a MOB-SLP_REQ message, or may besent unsolicited. The terminal shall assemble connections in powersaving classes and optionally activate them as described in the message.If for certain class activation is deferred (Activation=‘0’), the BS maysignal activation at later time in unsolicited MOB-SLP_RSP message.TABLE 2 Sleep-Response message format Syntax SizeMOB_SLP-RSP_Message_Format( ) {   Management message type = 51 8 bits  Number_of_Classes 4 bits   for (i = 0; i < Number_of_Classes; i++) {    Power_Saving_Class_Type 2 bits     Definition 1 bit      Operation 1bits     Reserved 2 bits     Power_Saving_Class_ID 6 bits     If(Operation = 1) {       Start_frame_number 8 bits     }     If(Definition = 1) {       initial-sleep window 8 bits       listeningwindow 8 bits       final-sleep window base 10 bits        final-sleepwindow exponent 3 bits       Number_of_CIDs 3 bits       for (i = 0; i <Number_of_CIDs; i++){         CID 16 bits        }    } }The parameters used are as follows:Power_Saving_Class_Type

Requested Power Saving Class type

Definition

1=Definition of Power Saving Class present

Operation

1=Activation of Power Saving Class

0=Deactivation of Power Saving Class (for types 1 and 2 only).

Power_Saving_Class_ID

Assigned Power Saving Class identifier. The ID shall be unique withinthe group of Power Saving Classes associated with the terminal. This IDmay be used in further MOB_SLP-REQ/RSP messages foractivation/deactivation of power saving procedure.

Start_Frame_Number

Start frame number for first sleep window.

Listening Interval

Assigned Duration of the terminal listening interval (measured inframes). For Power Saving Class type 2 it is not relevant and must beencoded as 0.

Initial-Sleep Window

Assigned initial duration for the sleep window (measured in frames). ForPower Saving Class type 2 it is not relevant and must be encoded as 0.

Final-Sleep Window Base

Assigned final value for the sleep interval (measured in frames). ForPower Saving Class type 2 it is not relevant and must be encoded as 0.For Power Saving Class type 2 it is the base for duration of singlesleep window requested by the message.

Final-Sleep Window Exponent

Assigned factor by which the final-sleep window base is multiplied inorder to calculate the final-sleep window. The following formula isused:final-sleep window=final-sleep window base×2ˆ(final-sleep windowexponent)

For power saving Class type 2 it is the exponent for the duration ofsingle sleep window requested by the message.

CID

CIDs of all connections comprising the Power Saving Class. This listshall contain either unicast connections or multicast connections ormanagement connections, but not combination of connections of differenttypes. If Basic CID is encoded, it means that all the terminal'sconnections are included in a single class.

-   CID=0 is reserved for management operations.

It will be appreciated that the above described methods may be varied inmany ways, including, changing the order of steps, and the exactimplementation used.

The present invention has been described using non-limiting detaileddescriptions of preferred embodiments thereof that are provided by wayof example and are not intended to limit the scope of the invention. Itshould be understood that features described with respect to oneembodiment may be used with other embodiments and that not allembodiments of the invention have all of the features shown in aparticular figure. Variations of embodiments described will occur topersons of the art. Furthermore, the terms “comprise,” “include,” “have”and their conjugates, shall mean, when used in the claims, “includingbut not necessarily limited to.” The scope of the invention is limitedonly by the following claims:

1. A method for effecting power saving in a subscriber's deviceassociated with a wireless network which comprises a base station and atleast said subscriber device, and wherein said subscriber's device isoperative to receive at least two different services each of which ischaracterized by one or more characteristics related to traffic demandsassociated with that service, which method comprises: classifying eachof said at least two different services based on their traffic demandrelated characteristics, into corresponding power saving classes,provided that there are at least two different power saving classesassociated with said at least two different services; for each of saidpower saving classes, determining required listening windows andrequired sleep windows; exchanging messages between said base stationand said subscriber's device for synchronizing parameters for carryingout a power saving procedure.
 2. A method according to claim 1, furthercomprising a step whereby said subscriber's device transmits a requestfor initiating the power saving procedure.
 3. A method according toclaim 1, wherein said classes' types are selected from the groupconsisting of: type 1, characterized in that the duration of each ofsaid sleep windows is not pre-defined and is derived from the durationof its preceding sleep window, while the duration of said listeningwindows remain constant; type 2, characterized in that all sleep windowsare of the same duration and are interleaved with listening windowshaving fixed duration; and type 3, characterized in that it comprises asingle sleep window and a single listening window.
 4. A method accordingto claim 3, wherein said type 1 class of power saving is furthercharacterized in that no traffic related to services comprised in saidclass is allowed to be exchanged during the duration of the sleepwindows and the listening windows.
 5. A method according to claim 3,wherein said type 2 class of power saving is further characterized inthat traffic related to services comprised in said class is allowed tobe exchanged during the duration of the listening windows.
 6. A methodaccording to claim 3, wherein said type 3 class of power saving isfurther characterized in that no traffic is allowed to be exchangedduring the duration of the sleep window.
 7. A method according to claim4, wherein the service provided is of said type 1 or type 2 classes, andwherein said method further comprises a step of deactivating said powersaving procedure by exchange of management messages between said basestation and said subscriber's device.
 8. A method according to claim 7,wherein said step of deactivating the power saving class of type 1 iscarried out in response to the occurrence of one or more of followingevents: said base station transmits during availability window anyamount of data over connection belonging to this power saving class;said subscriber's device transmits a request for non-zero amount ofbandwidth with respect to a service (connection) belonging to said powersaving class; said subscriber's device receives traffic indicationmessage indicating presence of buffered traffic addressed to saiddevice; and said subscriber's device has failed to receive trafficindication message during a certain timeout interval.
 9. A methodaccording to claim 7, wherein said step of deactivating the power savingclass of type 2 is carried out in response to explicit requesttransmitted in a form of pre-defined management message from said basestation and/or said subscriber's device.
 10. A method according to claim7, wherein said step of deactivating the power saving mode for type 3class of service is carried out in response to expiration of a listeningwindow.
 11. A base station adapted to operate in a wireless network andcomprising: an interface operative to allow communication between saidbase station and a communication network associated therewith; at leastone radio transceiver capable of transmitting communication traffictowards at least one subscriber device and receive communication traffictherefrom, wherein said base station is adapted to provide saidsubscriber with at least two different services, each of which ischaracterized by one or more characteristics related to traffic demandsassociated with that service; means operative to classify each of saidat least two different services based on their traffic-demand-relatedcharacteristics, into their corresponding power saving classes, providedthat there are at least two different power saving classes associatedwith services supported by the subscriber's device; at least oneprocessor adapted to: for each of said power saving classes, determinerequired listening windows and possible sleep windows; exchange messageswith said subscriber's device for synchronizing at least one parameterfor carrying out a power saving procedure; during provisioning of saidat least two different services, determine unavailability windows oftime for the subscriber's device in which no communication will beexchanged between said base station and said subscriber's device; andinitiating commands whereby said subscriber's device is required toactivate a power saving procedure for the duration of saidunavailability windows.
 12. A subscriber's terminal adapted to operatein a wireless network and to be receive at least two different services,each of which is characterized by one or more characteristics related totraffic demands associated with that service, and wherein saidsubscriber's terminal comprising: an interface operative to allowcommunication between said subscriber's terminal and a base station; atleast one radio transceiver operative to transmit communication traffictowards said base station and receive communication traffic therefrom;at least one processor adapted to exchange messages with said basestation for synchronizing at least one parameter for carrying out apower saving procedure; and a power controller operative to effect areduction in the power of said at least one radio transceiver for theduration of unavailability windows of time in which no communicationwill be exchanged between said base station and said subscriber'sterminal, in response to a pre-defined message received from said basestation.
 13. A subscriber's terminal according to claim 12, wherein saidat least one processor is further adapted to initiate a request fortransmitting a communication to said base station, by which the basestation is requested to evaluate whether, and/or when, said subscriber'sterminal may start a power saving procedure.
 14. A subscriber's terminalaccording to claim 12, further adapted to effect a power savingprocedure in response to an appropriate message and/or a signal receivedfrom said base station.